A comet is a small celestial body that orbits the sun. The comet nucleus consists of loose collections of ice, dust and small rocky particles. The comet tail is produced by the effects of solar radiation, and always points away from the sun. Comets may range from a kilometer to tens of kilometers wide.

There are many famous comets including Halley, Hale-Bopp, Kohoutek, Hyakutake, Shoemaker-Levy 9 (see here).

Universe Definition:"The Universe comprises everything that physically exists, the entirety of space and time, all forms of matter and energy, and the physical laws and constants that govern them." [Wikipedia]

Universe Facts:

The Universe was born about 13.73 (± 0.12) billion years ago.

Diameter of the observable universe is at least 93 billion light years.

Astrophysics Facts:"It may seem impossible that two galaxies on opposite sides can be separated by 93 billion light years after only 13 billion years, since special relativity states that matter cannot be accelerated to exceed the speed of light in a localized region of space-time. However, according to general relativity, space can expand with no intrinsic limit on its rate; thus, two galaxies can separate more quickly than the speed of light if the space between them grows. It is uncertain whether the size of the Universe is finite or infinite." [Wikipedia]

WMAP Image (see right):

The Cosmic Microwave Background Wilkinson Microwave Anisotropy Probe data seen over the full sky.

Average temperature - 2.725 Kelvin.

Colours represent the tiny temperature fluctuations.

Red regions are warmer and blue regions are colder (by about 0.0002 degrees).